# Cervical Disc Herniation and Radiculopathy

## Overview

Cervical radiculopathy is the compression or irritation of a cervical nerve root producing pain, sensory, and/or motor deficits in the corresponding dermatomal and myotomal distribution. It has an annual incidence of approximately 83 per 100,000 population, peaking in the 5th to 6th decade of life. The most common levels are C5-C6 and C6-C7, which together account for over 70% of cases. In younger patients the etiology is typically a soft disc herniation, while in older patients foraminal stenosis from uncovertebral and facet osteophytes causes spondylotic radiculopathy.

## Anatomy and Pathophysiology

### Cervical Disc Anatomy

The cervical disc consists of an annulus fibrosus (concentric lamellae of collagen fibers) surrounding the nucleus pulposus (a gelatinous core with high water content that desiccates with age). The uncovertebral joints (of Luschka), unique to the cervical spine, are posterolateral to the disc, and their hypertrophy contributes to foraminal stenosis. Because there is no true posterior longitudinal ligament coverage laterally, disc herniations tend to occur in a posterolateral direction.

### Neural Foraminal Anatomy

Cervical nerve roots exit above the correspondingly numbered pedicle (unlike the lumbar spine). Thus the C6 root exits through the C5-C6 foramen. The foramen is bounded by the pedicles superiorly and inferiorly, the uncovertebral joint anteriorly, and the facet joint posteriorly. The dorsal root ganglion sits within the foramen and is particularly sensitive to compression.

### Pathophysiology

The mechanism involves mechanical compression of the nerve root combined with inflammatory mediators (TNF-alpha, IL-1, IL-6) released from herniated disc material. Dorsal root ganglion compression may produce disproportionate pain, and venous congestion with edema of the nerve root contributes to symptoms.

## Clinical Presentation

### Symptoms

Patients present with neck pain often radiating to the periscapular region, radicular arm pain in a dermatomal distribution, numbness or tingling or paresthesias, and weakness in the corresponding myotome.

### Root-Specific Syndromes

The C5 root (C4-C5 disc level) produces lateral shoulder and upper arm pain, deltoid and biceps weakness, and diminished biceps reflex. The C6 root (C5-C6 disc level) causes lateral forearm, thumb, and index finger pain, biceps and wrist extension weakness, and diminished brachioradialis reflex. The C7 root (C6-C7 disc level) produces middle finger and dorsal forearm pain, triceps, wrist flexion, and finger extension weakness, and diminished triceps reflex. The C8 root (C7-T1 disc level) causes ring and small finger with medial forearm pain and finger flexion and hand intrinsic weakness, without a reliable reflex. The T1 root (T1-T2 disc level) produces medial arm pain and hand intrinsic weakness.

| Root | Disc Level | Pain Distribution | Motor Weakness | Reflex |
|------|-----------|-------------------|----------------|--------|
| C5 | C4-C5 | Lateral shoulder, upper arm | Deltoid, biceps | Biceps |
| C6 | C5-C6 | Lateral forearm, thumb, index finger | Biceps, wrist extension | Brachioradialis |
| C7 | C6-C7 | Middle finger, dorsal forearm | Triceps, wrist flexion, finger extension | Triceps |
| C8 | C7-T1 | Ring/small finger, medial forearm | Finger flexion, hand intrinsics | None reliable |
| T1 | T1-T2 | Medial arm | Hand intrinsics | None |

### Physical Examination

The Spurling test (axial compression with head extended and rotated toward the symptomatic side) reproduces radicular pain with high specificity (~95%) but lower sensitivity (~50%). The shoulder abduction relief sign demonstrates pain relief when the patient places the hand on the head, reducing nerve root tension. Lhermitte sign (electric sensation down the spine with neck flexion) suggests cord involvement and raises concern for myelopathy. The examiner should always check for upper motor neuron signs (Hoffman sign, clonus, hyperreflexia) to exclude concomitant myelopathy.

## Diagnostic Imaging

### MRI (Study of Choice)

T2-weighted sequences best demonstrate disc herniation and nerve root compression. The study evaluates for cord signal change suggesting myelopathy and assesses foraminal narrowing on parasagittal views. Disc abnormalities are common in asymptomatic individuals, making clinical correlation essential.

### CT Myelography

CT myelography is the gold standard for bony detail and dynamic canal assessment. It is indicated when MRI is contraindicated or non-diagnostic and provides superior delineation of osteophytic foraminal stenosis.

### Plain Radiographs

Radiographs assess alignment, disc space narrowing, and osteophyte formation. Flexion-extension views are obtained if instability is suspected. They have a limited role in the acute radiculopathy workup.

### Electrodiagnostics (EMG/NCS)

These are helpful when the diagnosis is uncertain or multiple levels are involved, differentiating radiculopathy from peripheral neuropathy or plexopathy. Fibrillation potentials and positive sharp waves indicating active denervation appear more than 2-3 weeks after onset.

## Conservative Management

The natural history is favorable, with 75-90% of patients improving with conservative measures within 6-12 weeks. Treatment includes NSAIDs, short courses of oral corticosteroids, neuropathic agents (gabapentin, pregabalin), and muscle relaxants. Physical therapy employs cervical traction, isometric strengthening, and postural training. Cervical epidural steroid injection (transforaminal or interlaminar) may provide temporary relief, though evidence for long-term benefit is limited. A cervical collar is used only for short-term (1-2 weeks) acute pain relief; prolonged use is discouraged.

## Surgical Management

### Indications

Surgical intervention is indicated for progressive motor deficit, intractable pain despite adequate conservative management (typically 6-12 weeks), evidence of significant cord compression or early myelopathy, and severe weakness at presentation (MRC grade 3 or less).

### Anterior Cervical Discectomy and Fusion (ACDF)

ACDF is the most commonly performed procedure for cervical radiculopathy. The Smith-Robinson approach uses a left-sided transverse skin incision, dissecting medial to the sternocleidomastoid, retracting the esophagus and trachea medially and the carotid sheath laterally. Complete discectomy with removal of posterior osteophytes and decompression of the foramen is performed. An interbody graft (allograft, PEEK cage, or autograft) is placed with or without an anterior plate. Fusion rates exceed 95% for single-level procedures. Complications include dysphagia (the most common, usually transient), recurrent laryngeal nerve injury, esophageal perforation (rare), and adjacent segment disease (long-term).

### Posterior Cervical Foraminotomy

This keyhole laminoforaminotomy via a posterior approach preserves motion without requiring fusion. It is best suited for lateral or foraminal soft disc herniations and foraminal stenosis, but is not appropriate for central disc herniations, significant kyphosis, or instability. It can be performed open or with minimally invasive techniques using tubular retractors. Its advantages include no dysphagia risk, motion preservation, and no need for instrumentation. The disadvantage is limited access to central pathology and risk of kyphosis if too much facet is resected (more than 50% of the facet should be preserved).

### Cervical Disc Arthroplasty

Disc arthroplasty is a motion-preserving alternative to ACDF. FDA-approved devices include the Mobi-C, Prestige LP, and ProDisc-C. Multiple RCTs show non-inferiority or superiority to ACDF at long-term follow-up. Contraindications include significant facet arthropathy, instability, ossification of the PLL, and osteoporosis. The theoretical advantage of reduced adjacent segment degeneration remains debated.

## Outcomes

ACDF achieves greater than 90% good-to-excellent outcomes for radiculopathy. Posterior foraminotomy has 85-95% success rates. Disc arthroplasty produces comparable outcomes to ACDF with potential motion preservation. Prognostic factors for better outcomes include shorter duration of symptoms, younger age, and absence of myelopathy.

<image>Axial T2-weighted MRI at the C5-C6 level demonstrating a left posterolateral disc herniation compressing the exiting C6 nerve root in the neural foramen, with the thecal sac displaced to the right and effacement of the left lateral recess and foramen</image>

<image>Intraoperative photograph of an anterior cervical discectomy and fusion (ACDF) procedure showing the Smith-Robinson approach with self-retaining retractors holding the esophagus and trachea medially and the carotid sheath laterally, exposing the anterior cervical spine with the disc space identified and Caspar pins placed for distraction</image>

<image>Lateral cervical spine radiograph following a single-level ACDF at C5-C6 showing an interbody PEEK cage with anterior cervical plate and four screws, demonstrating restoration of disc height and lordotic alignment</image>

## Clinical Pearls

The distinction between radiculopathy and myelopathy is critical: radiculopathy may be observed or treated electively, while myelopathy with progressive deficits warrants more urgent intervention. The Spurling test is highly specific, and a positive test strongly supports the diagnosis of radiculopathy. C5 palsy can occur as a postoperative complication after ACDF or posterior decompression (incidence 2-5%), likely due to nerve root tethering after cord shift. Recurrent laryngeal nerve palsy risk is higher with right-sided anterior approaches due to the variable course of the right RLN, making a left-sided approach preferred for primary cases. Adjacent segment disease after ACDF occurs at approximately 2-3% per year; disc arthroplasty may reduce but does not eliminate this risk. Always examine for Hoffman sign and clonus in any patient presenting with arm radiculopathy to avoid missing concomitant myelopathy.

## References
- Caridi JM, et al. "Cervical Radiculopathy: A Review." *HSS J*. 2011;7(3):265-272.
- Herkowitz HN, et al. "A Comparison of Anterior Cervical Fusion, Cervical Laminectomy, and Cervical Laminoplasty for the Treatment of Cervical Spondylotic Radiculopathy and Myelopathy." *Spine*. 1988;13(7):774-780.
- Murrey D, et al. "Results of the Prospective, Randomized, Controlled Multicenter FDA Investigational Device Exemption Study of the ProDisc-C Total Disc Replacement versus Anterior Discectomy and Fusion." *Spine J*. 2009;9(4):275-286.
- Adamson TE. "Microendoscopic Posterior Cervical Laminoforaminotomy for Unilateral Radiculopathy." *J Neurosurg*. 2001;95(1 Suppl):51-57.
- Traynelis VC, et al. "Cervical Disc Arthroplasty." *Neurosurgery*. 2017;81(5):713-726.